Genezzo-Contrib-Clustered
=========================
Shared data cluster support for Genezzo
Genezzo is an extensible database with SQL and DBI. It is written in Perl.
Basic routines inside Genezzo are overridden via Havok SysHooks. Override
routines provide support for shared data clusters. Routines
provide transactions, distributed locking, undo, and recovery.
INSTALLATION
To install this module type the following:
perl Makefile.PL
make
make test
make install
To prepare for use of Genezzo::Clustered
genprepundo.pl
gendba.pl
>@havok.sql
>@syshook.sql
>@clustered.sql
LIMITATIONS
This is pre-alpha software; don't use it to store any data you hope
to see again!
Transactions, Rollback, etc. are not fully implemented. Process death
and necessary cleanup is not detected.
DEPENDENCIES
This module requires these other modules and libraries:
Genezzo
FreezeThaw
OpenDLM
SEE ALSO
For more information, please visit the Genezzo homepage
at http://www.genezzo.com
also
http://eric_rollins.home.mindspring.com/genezzo/ClusteredGenezzoDesign.html
http://eric_rollins.home.mindspring.com/genezzo/cluster.html
http://opendlm.sourceforge.net/
TODO
1) [Genezzo fix done]
2) [Genezzo update] Need a exception mechanism when SQL is run to catch
errors such as running out of disk space. Currently multi-row
SQL statements can result in partial results on disk when system
runs out of disk space.
3) Use new exception mechanism (above) to handle deadlock with DLM.
Currently program exits on any error from OpenDLM. Need to modify
inline::C interface to provide deadlock return code distinct from
other errors. Need to modify GLock Perl code to throw SQL exception.
4) [Genezzo update done]
5) done.
6) [Genezzo update] Need way to invalidate entire buffer cache.
Simply release all blocks, don't write them to disk (disk write
should already have been done in commit case).
7) Invalidate buffer cache (using new mechanism above) before releasing
all locks on commit or rollback. Actually only invalidate
non-system tablespace portion, see below.
8) [Genezzo update done]
9) done
10) [Genezzo fix] fix "mystery" writes. These bogus writes create
unnecessary write locks, generate unnecessary undo, and confuse
rollback code. Solution may be to attach syshook to new attachment
point instead of Genezzo::BufCa::DirtyScalar::STORE. Yes, some of
the writes are not "mysteries". They occur when a pre-existing
buffer cache block is reused -- the reloading of new data from disk
or memory into the block triggers the STORE callback. The cure
is to attach the syshook in a more intelligent location that is
aware of the different cases.
11) [Genezzo update] complete tablespace support.
12) Use tablespace support (above) to restrict locking to non-system
tablespace tables. Otherwise we need to lock additional blocks
(for system tables) already read at startup prior to syshook
initialization. And locking system tables prevents other
instances from running in parallel. [this may not solve problems...]
13) [Genezzo update] add pre-havok command line param which specifies
routine to run prior to opening database.
14) Use pre-havok (above) to perform recovery prior to opening database.
Havok/syshook routines won't run if database cannot be opened due
to corruption.
13) [Genezzo redesign] Storing table directory and free space list in
block zero of each tablespace prevents any concurrency of writes
with reads. Also cached structures become invalid whenever block
zero is written.
14) [Genezzo refactoring] Move Verify and Update checksum routines
out of Genezzo::BufCA::BCFile::_filereadblock and _filewriteblock
and into Util.
15) Modify VerifyChecksum and UpdateChecksum to use Util routines.
99) After the above, complete rest of development per Design Document:
a) [Done] Detect blocks needing recovery via process_id in block.
b) [Done] Recover dead processes
c) etc...
100) Recognize incomplete undo blocks and read buddy block instead.
COPYRIGHT AND LICENCE
Copyright (C) 2005 by Eric Rollins. All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Address bug reports and comments to rollins@acm.org